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import functools |
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import inspect |
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from typing import Dict, Type, Union, Any, TypeVar, Callable |
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from lagom.util.functional import arity |
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from .exceptions import UnresolvableType, InvalidDependencyDefinition |
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from .definitions import Resolver, Construction, Singleton, Alias, DEFINITION_TYPES |
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UNRESOLVABLE_TYPES = [str, int, float, bool] |
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X = TypeVar("X") |
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DepDefinition = Any |
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class Container: |
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_registered_types: Dict[Type, Resolver] = {} |
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def define(self, dep: Union[Type[X], Type], resolver: DepDefinition) -> None: |
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self._registered_types[dep] = self._normalise(resolver) |
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def resolve(self, dep_type: Type[X], suppress_error=False) -> X: |
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try: |
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if dep_type in UNRESOLVABLE_TYPES: |
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raise UnresolvableType(f"Cannot construct type {dep_type}") |
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registered_type = self._registered_types.get(dep_type, dep_type) |
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if isinstance(registered_type, Singleton): |
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return self._load_singleton(registered_type) |
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return self._build(registered_type) |
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except UnresolvableType as inner_error: |
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if not suppress_error: |
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raise UnresolvableType( |
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f"Cannot construct type {dep_type.__name__}" |
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) from inner_error |
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return None # type: ignore |
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def partial(self, func: Callable) -> Callable: |
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spec = inspect.getfullargspec(func) |
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bindable_deps = self._infer_dependencies(spec, suppress_error=True) |
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return functools.partial(func, **bindable_deps) |
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def __getitem__(self, dep: Type[X]) -> X: |
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return self.resolve(dep) |
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def __setitem__(self, dep: Type, resolver: DepDefinition): |
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self.define(dep, resolver) |
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def _normalise(self, resolver: DepDefinition) -> Resolver: |
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if type(resolver) in DEFINITION_TYPES: |
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return resolver |
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elif inspect.isfunction(resolver): |
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return self._build_lambda_constructor(resolver) |
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elif not inspect.isclass(resolver): |
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return Singleton(lambda: resolver) # type: ignore |
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else: |
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return Alias(resolver) |
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def _build_lambda_constructor(self, resolver: Callable) -> Construction: |
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artiy = arity(resolver) |
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if artiy == 0: |
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return Construction(resolver) |
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if artiy == 1: |
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return Construction(functools.partial(resolver, self)) |
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raise InvalidDependencyDefinition(f"Arity {arity} functions are not supported") |
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def _build(self, dep_type: Any) -> Any: |
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if isinstance(dep_type, Alias): |
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return self.resolve(dep_type.alias_type) |
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if isinstance(dep_type, Construction): |
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return dep_type.construct() |
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return self._reflection_build(dep_type) |
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def _reflection_build(self, dep_type: Type[X]) -> X: |
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spec = inspect.getfullargspec(dep_type.__init__) |
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sub_deps = self._infer_dependencies(spec) |
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return dep_type(**sub_deps) # type: ignore |
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def _infer_dependencies(self, spec: inspect.FullArgSpec, suppress_error=False): |
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sub_deps = { |
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key: self.resolve(sub_dep_type, suppress_error=suppress_error) |
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for (key, sub_dep_type) in spec.annotations.items() |
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} |
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filtered_deps = {key: dep for (key, dep) in sub_deps.items() if dep is not None} |
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return filtered_deps |
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def _load_singleton(self, singleton: Singleton): |
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if singleton.has_instance: |
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return singleton.instance |
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return singleton.set_instance(self._build(singleton.singleton_type)) |
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meadsteve /
lagom
